lib/livepatch/test_klp_state.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 // Copyright (C) 2019 SUSE
0003
0004 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
0005
0006 #include <linux/slab.h>
0007 #include <linux/module.h>
0008 #include <linux/kernel.h>
0009 #include <linux/printk.h>
0010 #include <linux/livepatch.h>
0011
0012 #define CONSOLE_LOGLEVEL_STATE 1
0013 /* Version 1 does not support migration. */
0014 #define CONSOLE_LOGLEVEL_STATE_VERSION 1
0015
0016 static const char *const module_state[] = {
0017     [MODULE_STATE_LIVE] = "[MODULE_STATE_LIVE] Normal state",
0018     [MODULE_STATE_COMING]   = "[MODULE_STATE_COMING] Full formed, running module_init",
0019     [MODULE_STATE_GOING]    = "[MODULE_STATE_GOING] Going away",
0020     [MODULE_STATE_UNFORMED] = "[MODULE_STATE_UNFORMED] Still setting it up",
0021 };
0022
0023 static void callback_info(const char *callback, struct klp_object *obj)
0024 {
0025     if (obj->mod)
0026         pr_info("%s: %s -> %s\n", callback, obj->mod->name,
0027             module_state[obj->mod->state]);
0028     else
0029         pr_info("%s: vmlinux\n", callback);
0030 }
0031
0032 static struct klp_patch patch;
0033
0034 static int allocate_loglevel_state(void)
0035 {
0036     struct klp_state *loglevel_state;
0037
0038     loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
0039     if (!loglevel_state)
0040         return -EINVAL;
0041
0042     loglevel_state->data = kzalloc(sizeof(console_loglevel), GFP_KERNEL);
0043     if (!loglevel_state->data)
0044         return -ENOMEM;
0045
0046     pr_info("%s: allocating space to store console_loglevel\n",
0047         __func__);
0048     return 0;
0049 }
0050
0051 static void fix_console_loglevel(void)
0052 {
0053     struct klp_state *loglevel_state;
0054
0055     loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
0056     if (!loglevel_state)
0057         return;
0058
0059     pr_info("%s: fixing console_loglevel\n", __func__);
0060     *(int *)loglevel_state->data = console_loglevel;
0061     console_loglevel = CONSOLE_LOGLEVEL_MOTORMOUTH;
0062 }
0063
0064 static void restore_console_loglevel(void)
0065 {
0066     struct klp_state *loglevel_state;
0067
0068     loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
0069     if (!loglevel_state)
0070         return;
0071
0072     pr_info("%s: restoring console_loglevel\n", __func__);
0073     console_loglevel = *(int *)loglevel_state->data;
0074 }
0075
0076 static void free_loglevel_state(void)
0077 {
0078     struct klp_state *loglevel_state;
0079
0080     loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
0081     if (!loglevel_state)
0082         return;
0083
0084     pr_info("%s: freeing space for the stored console_loglevel\n",
0085         __func__);
0086     kfree(loglevel_state->data);
0087 }
0088
0089 /* Executed on object patching (ie, patch enablement) */
0090 static int pre_patch_callback(struct klp_object *obj)
0091 {
0092     callback_info(__func__, obj);
0093     return allocate_loglevel_state();
0094 }
0095
0096 /* Executed on object unpatching (ie, patch disablement) */
0097 static void post_patch_callback(struct klp_object *obj)
0098 {
0099     callback_info(__func__, obj);
0100     fix_console_loglevel();
0101 }
0102
0103 /* Executed on object unpatching (ie, patch disablement) */
0104 static void pre_unpatch_callback(struct klp_object *obj)
0105 {
0106     callback_info(__func__, obj);
0107     restore_console_loglevel();
0108 }
0109
0110 /* Executed on object unpatching (ie, patch disablement) */
0111 static void post_unpatch_callback(struct klp_object *obj)
0112 {
0113     callback_info(__func__, obj);
0114     free_loglevel_state();
0115 }
0116
0117 static struct klp_func no_funcs[] = {
0118     {}
0119 };
0120
0121 static struct klp_object objs[] = {
0122     {
0123         .name = NULL,   /* vmlinux */
0124         .funcs = no_funcs,
0125         .callbacks = {
0126             .pre_patch = pre_patch_callback,
0127             .post_patch = post_patch_callback,
0128             .pre_unpatch = pre_unpatch_callback,
0129             .post_unpatch = post_unpatch_callback,
0130         },
0131     }, { }
0132 };
0133
0134 static struct klp_state states[] = {
0135     {
0136         .id = CONSOLE_LOGLEVEL_STATE,
0137         .version = CONSOLE_LOGLEVEL_STATE_VERSION,
0138     }, { }
0139 };
0140
0141 static struct klp_patch patch = {
0142     .mod = THIS_MODULE,
0143     .objs = objs,
0144     .states = states,
0145     .replace = true,
0146 };
0147
0148 static int test_klp_callbacks_demo_init(void)
0149 {
0150     return klp_enable_patch(&patch);
0151 }
0152
0153 static void test_klp_callbacks_demo_exit(void)
0154 {
0155 }
0156
0157 module_init(test_klp_callbacks_demo_init);
0158 module_exit(test_klp_callbacks_demo_exit);
0159 MODULE_LICENSE("GPL");
0160 MODULE_INFO(livepatch, "Y");
0161 MODULE_AUTHOR("Petr Mladek <pmladek@suse.com>");
0162 MODULE_DESCRIPTION("Livepatch test: system state modification");